Here's why:

* Rock Breakdown: Gravel is formed when larger rocks are broken down by processes like weathering, erosion, and transportation.

* Size Matters: Gravel is defined by its size – it's typically larger than sand but smaller than boulders.

* Composition: Gravel can be composed of various types of rock, like granite, limestone, sandstone, or even volcanic rock.

So, while gravel is not a specific type of rock itself, it's essentially a collection of broken-down rock fragments.